1. Field of the Invention
This invention relates to metallurgical furnaces of the type used to reheat previously shaped billets, wherein the shaped billets to be treated move along rails supported by water cooled tubular support members, and more particularly, to an assembly of pre-burned ceramic refractory members for use in protecting the water cooled supports in the furnace.
2. Description of the Prior Art
In the preparation of steel billets, slabs and other metal workpieces preparatory to further shaping or forming, it is customary to subject the workpieces to direct heating while passing through a furnace. The billets, moreover, move through the furnace on skid rails which are supported from below by horizontal and vertical water cooled tubular support members. With this construction, fuel may be burned both above and below the skid rails so that the billets or workpieces may be uniformly heated from all sides.
In the continuous furnace of the type described above, the billets or workpieces are generally heated to a temperature on the order of 2,000.degree. F. Clearly, the skid rails and the support tubes must be protected by sufficient insulating material to minimize the heat lost to the water cooled tubes, and further, to minimize the erosion and corrosion of the tubes resulting from the high temperatures and oxidation environment encountered in the furnace.
In the past, it has been recognized as desirable to insulate these water cooled support members by applying a lining or covering of fibrous insulating material, as shown in Balaz et al U.S. Pat. No. 3,226,101, or by applying ceramic tiles assembled in encircling relationship to the water cooled support members or the skid rails as shown in the patents to McCullough U.S. Pat. No. 3,055,651 and Nicol U.S. Pat. No. 3,881,864. In general, however, it has been found that the combination of both fibrous insulation and ceramic tiles covering the insulation provide the best protection for the water cooled supports. That is, the fibrous insulation thermally insulates the support members, and the outer covering of ceramic refractory tiles protect the fibrous insulation from the deleterious effects of the furnace gases. In this combination of insulation and ceramic tiles, the encircling ceramic tiles are subjected to intense vibrational loadings caused by movement of the slabs and large thermal stresses as a result of temperature gradients therethrough which may cause cracking of the tiles. The internal stresses, moreover, are more pronounced in the vicinity of the engagement means employed to interlock adjacent tiles or individual tiles to the tubular support members. In general, the aforementioned engagement means consists of a metallic stud welded to the tubular support member and/or interlocking lug members formed in the ceramic tile, such as shown in the Schmidt U.S. Pat. No. 2,436,452. Furthermore, the complex arrangement generally employed in holding the ceramic tile members together about the tubular support member renders replacement of a single ceramic section quite difficult.
Necessarily, the tiles must be segmental not only for ease of installation, but also to provide for thermal expansion and contraction in the ceramic and between the ceramic and the metal of the pipes, during furnace operations.
Therefore, there is a need to provide industry with an insulation and protection arrangement which economically and efficiently insulates the tubular members, protects the insulation from the furnace gases, minimizes the magnitude of internal stress and loading imposed thereon and which provides a simple method of replacing a single ceramic tile section of the protection arrangement.